This invention relates to a sputtering target for use in formation of conductive thin films on semiconductor elements such as LSI chips and the like, and more particularly it relates to a sputtering target by which thickness of the thin films can be made uniform and by which scatter of sheet resistance in the thin films can be minimized.
For example, in manufacturing MOS type LSI gate electrodes, conductive thin films of a high-melting metal or the like are formed on the surfaces of LSI chips. As a means for forming the thin films, a sputtering process is usually applied.
In this case, a suitable sputtering target is selected from those having various morphologies in compliance with the kind of thin films to be formed.
For example, when the thin film is formed of a single metal prepared by a melting process, there is used, as the sputtering target, a single block comprising a metal prepared by a melting process and having an optional shape, such as a disk plate, a rectangular plate or the like on the whole, or a combined block having an optional shape, such as a disk plate, a rectangular plate or the like on the whole and comprising a combination of a plurality of wedge-shaped units composed of the above-mentioned metal.
Further, when thin films are formed with an alloy such as a silicide, there is used, as the sputtering target, an alloy block comprising an alloy prepared by a melting process and having an optional shape, such as a disk plate, a rectangular plate or the like on the whole, or a combined block having an optional shape, such as a disk plate, a rectanguar plate or the like on the whole and comprising an optional combination of a plurality of wedge-shaped or square, bar-shaped single blocks composed of metals constituting the alloy prepared by the melting process.
Important requirements regarding a sputtering process are that film resistance (sheet resistance, .OMEGA./.quadrature.) of the formed thin film must not exceed a standard level and that scatter of sheet resistance values at certain positions on the surface of the formed thin film be narrow. The sheet resistance may be measured in accordance with a four-probe method.